A great way to re-purpose these cells for rebuilds that are only limited by your imagination.
Good/Bad Batteries: What's the difference?
Not all batteries are equal, and the following should be taken into account when deciding on which batteries to use. They are a big investment, and if they fail, you will be left with no power.
1/. Batteries produce different power at different rates of discharge. In general, an off-grid battery will need to discharge over a relatively short period, perhaps twelve hours, and then recharge the next day. So, the most accurate way to determine the battery's capacity is to work on a 10-hour or C10 rating. Therefore, a C10 1000AH battery, assuming only 30% Depth of Discharge (DOD), is taking 30% out of the battery and leaving 70% in.
1000Ah @ 30% is 300AH divided by 10 hours, which is 30 Amps an hour.
2/. Most importantly, the rating to consider is the cyclic life. All batteries have a cyclic life, at the end of which the battery is spent and can't hold current anymore. The battery life is directly proportional to the DOD, and most battery manufacturers will give a graph or values of cyclic life. Cheaper batteries have very poor or low cyclic life. For example, a battery with 1500 cycles @ 30% discharge will only cycle, discharge, and charge again 1500 times divided by the days of the year (365) for 4 years, at which time they need to be replaced. A good and true deep cycle cyclic battery might have 3500-4000 cycles @ 30% DOD and will last twice as long.
3/. The health of a battery is based on three fundamental attributes:
Capacity, the ability to store energy. Capacity is the leading health indicator of a battery.
Internal resistance, the ability to deliver current.
Self-discharge, an indicator of mechanical integrity.
When making these measurements, you must consider the type and accuracy of the equipment used and the ambient and battery temperature.
4/. Most importantly, the individual cells' weight greatly affects longevity and the battery's ability to cycle, discharge, and recharge. A battery is a chemical storage device that uses chemistry to store electrons or electricity. The most common batteries until recently have been lead-based: lead and acid and the chemical reaction between the store or release electricity. The more lead and acid inside the battery, the greater the amounts of storage and aids the battery in recovering from overcharge and/or discharge events. Check the weight of the battery (Lithium, Ni-Cads, lead/acid); if it weighs 30% less than its counterpart, it stands to reason that it has 30% less chemistry/lead, and it won't last as long.
These cells are fully capacity-tested by charging to a max 4.15v, then stored for 6–8 weeks, voltage rechecked for self-discharge, and then discharged to 3.25v, which allows the cell to return its internal voltage to around 3.65v for shipping via Australia Post. Any cells showing a resistance in excess of 100 mΩ are disposed of.
We provide the resulting available mAh as a guide for the balancing of your multi-cell battery builds; runtime can be increased or decreased by changing your charging regime.
The health of a battery is based on three fundamental attributes:
- Capacity, the ability to store energy. Capacity is the leading health indicator of a battery.
- Internal resistance, the ability to deliver current.
- Self-discharge, indicator of mechanical integrity.
When making these measurements, you must consider the type and accuracy of equipment used, as well as the ambient and battery temperature.
There are many chemical combos that change the way lithium batteries produce energy. Not choosing CAREFULLY can be disastrous.
This table shows the most common 18650 battery chemistry and their abbreviations:
|Lithium manganese oxide
|Lithium manganese nickel
|Lithium nickel cobalt aluminium oxide
|Lithium nickel cobalt oxide
|Lithium cobalt oxide
|Lithium iron phosphate
Each chemistry has its own advantages and disadvantages. Let's go through each chemistry and their common 18650 models and understand what exactly these names mean…
An 18650 li-ion battery consists of three parts: the cathode, the anode, and the electrolyte.
The anode of all 18650 li-ion batteries is basically the same: carbon/silicon and graphite. The cathode, however, is where batteries differ, and it's what gives each model its unique characteristics. The chemical formulas in the table refer to the battery's cathode.
One of the trade-offs with cathode chemistry is between energy, capacity, cycle life, and safety. For instance, ICR (cobalt-based) chemistries are both high energy and high capacity, but not very safe. IMR is safer, but has lower capacity than ICR. Adding nickel to manganese (IMR) gives it a higher specific energy.
Now that we know what each chemistry means, let's look at each specific chemistry. Re-purposing Rebuilds